Encapsulated bacteriophage formulation

ABSTRACT

An encapsulated bacteriophage formulation and a method for preparing encapsulated bacteriophage formulation is provided. The method for producing the encapsulated bacteriophage composition involves injection of a molten coating substance comprising stearic acid and palmitic acid present at a ratio of 50:50, into a granulator chamber containing immobilized bacteriophages. The immobilized bacteriophage are agitated by rotation of a base of the chamber and swept by a flow of air at a temperature of between 10° C. and 50° C.

This application is a Continuation application of U.S. patent application Ser. No. 11/666,706, filed May 20, 2008, the entire contents of which are hereby incorporated herein by reference. U.S. patent application Ser. No. 11/666,706 is a National Stage application of International Application No. PCT/CA2005/001679, filed Nov. 2, 2005, the entire contents of which are hereby incorporated herein by reference. International Application No. PCT/CA2005/001679 claims the benefit of U.S. Provisional Application No. 60/624,576, filed Nov. 2, 2004, the entire contents of which are hereby incorporated herein by reference.

The present invention relates to an encapsulated bacteriophage formulation. More particularly, the present invention pertains to an encapsulated bacteriophage formulation and methods for preparing the encapsulated bacteriophage formulation.

BACKGROUND OF THE INVENTION

Bacteriophage therapy has the potential to provide an effective method to control the undesirable multiplication of various strains of bacteria. However, to be commercially viable, the bacteriophages themselves must show a certain degree of stability to allow for storage.

Various methods have been used to store and protect phage, including freezing at low temperatures, lyophilising, and storing in liquid medium. All methods have shown varying degrees of success at maintaining a high titer of viable bacteriophages.

Prouty (1953, Appl Microbiol, 1:250-351) reported that desiccated bacteriophage of lactic acid Streptococci remained viable at 0° C. for 42 months, at 37° C. for 72 months and at 12° C. and 25° C. for at least 78 months. However, there is no mention of the effect of storing desiccated bacteriophage on the titer of the bacteriophage.

Keogh and Pettingill (1966, Appl Microbiol, 14:4421-424) show that bacteriophages for lactic acid Streptococci in the presence of whey protein are resistant to freezing and cold storage. Phage stored at 4° C. and −18° C. showed little reduction in the bacteriophage titer; freeze-thaw cycles also showed no significant loss of titer. Warren and Hatch (1969, Appl Microbiol, 17:256-261) report a significant decrease in the titer and viability of a bacteriophage suspension stored (without stabilizers) at 4° C., while storage at −20° C. and 20° C. resulted in the greatest survival of phage. They also report that long term storage of bacteriophages at −20° C. tends to result in the formation of clumps.

Jepson and March (2004, Vaccine, 22:2413-2419) disclose that a liquid suspension of bacteriophages (in either SM buffer or a 1/200 dilution of SM buffer in water) was stable for 6 months at 4° C. and −70° C., with the phage remaining unaffected by freeze-thawing. Increased temperature, between 20° C. and 42° C., resulted in a significant loss of titre. Lyophilisation and immediate reconstitution of bacteriophages in the presence or absence of stabilizers resulted in a loss of titre of 80-95%. Of the bacteriophages remaining following lyophilization in the presence of dry skim milk powder, storage at temperatures between 20° C. and 42° C. resulted in a loss of titre similar to that of the liquid suspension. However, lyophilization in the presence of trehalose resulted in an increase in half-life of bacteriophage between 20° C. and 42° C. The effect of pH of the storage medium was also examined. There was no change in bacteriophage titer over a 24 hour period at pH 3-11. However, the titer dropped rapidly when stored for 5 minutes at pH values below 2.4.

Freezing or lyophilisation of bacteriophage suspensions, or bacteriophage suspensions optionally containing stabilizers, are inconvenient methods that require specialized equipment and add to the cost of a commercial preparation. While it may be in certain circumstances desirable to be able to store bacteriophages in a desiccated state, the process of lyophilization results in a significant loss of titre. Alternative methods for bacteriophage stabilization are required

SUMMARY OF THE INVENTION

The present invention relates to an encapsulated bacteriophage formulation. More particularly, the present invention pertains to an encapsulated bacteriophage formulation and methods for preparing the encapsulated bacteriophage formulation.

It is an object of the present invention to provide an encapsulated bacteriophage formulation.

The present invention provides a method for producing an encapsulated bacteriophage formulation comprising,

injecting a molten coating substance comprising a 50:50 solution of palmitic and stearic acids, at a temperature of between about 20° C. and about 80° C. into a chamber containing bacteriophage immobilized on skim milk powder, the bacteriophage immobilized on skim milk powder agitated by rotation of a base of the chamber and swept by a flow of air at a temperature of between 10° C. and 50° C., the flow of air having a speed such that the chamber temperature is between about 30° C. to about 55° C., to produce an encapsulated bacteriophage formulation.

The present invention also pertains to the method described above wherein the speed of rotation of the base of said chamber may be between 50 and 500 rpm. In the method as described above, the coating substance may also have a melting point of between 30° C. and 80° C. The present invention also pertains to the above method, wherein the injection temperature may be between 60° C. and 120° C. In the above method, the temperature in the chamber may be between 30° C. and 55° C. Additionally, in the method as described above, the proportion of the injected coating substance may be between 10 and 99% by weight of the encapsulated bacteriophage formulation.

The present invention also provides an encapsulated bacteriophage formulation comprising an bacteriophage immobilized on skim milk powder and encapsulated with a coating consisting of stearic acid and palmitic acid present at a ratio of 50:50.

The encapsulated bacteriophage formulation of the present invention is resistant to extended periods of exposure to low pH that would otherwise render the bacteriophage non-viable. Encapsulated antibacterial compositions of the present invention may be used for any suitable purpose that requires a bacteriophage preparation, for example, the encapsulated bacteriophage composition may be added to animal feed and fed to an animal. In this case, the encapsulation of the bacteriophages results in protecting the bacteriophages from stomach acids and increasing the duration of bacteriophage release within the gut of the animal. The antibacterial compositions of the present invention may be used for veterinary purposes.

This summary of the invention does not necessarily describe all necessary features of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings wherein:

FIG. 1 shows the effect of encapsulation on bacteriophage activity. Phage titers before and after encapsulation are shown.

FIG. 2A shows the effect of low pH on the stability of encapsulated phages. Encapsulated phage titers were determined before and after grinding. All phage concentrations have been corrected for the weight of encapsulated material. FIG. 2B shows the effect of low pH on the infectivity of phage. The phages were neither immobilized nor encapsulated.

DESCRIPTION OF PREFERRED EMBODIMENT

The present invention relates to stabilized bacteriophage formulations. More particularly, the present invention pertains to stabilized bacteriophage formulations and methods for preparing stabilized bacteriophage formulations.

The following description is of a preferred embodiment.

The present invention provides an encapsulated bacteriophage formulation. The present invention also provides a method for producing an encapsulated bacteriophage formulation comprising encapsulating immobilized bacteriophages.

The encapsulated bacteriophage formulation may be used in a variety of ways for the control of bacterial growth, and may be used for a variety of applications. For example, the antibacterial composition may be encapsulated and used as a feed additive or as an oral treatment for the control of bacteria within a human, a mammal, or an avian species.

The term “bacteriophage” or “phage” is well known in the art and generally indicates a virus-like particle that infects bacteria. Phages are parasites that multiply inside bacterial cells by using some or all of the hosts' biosynthetic machinery, and can either be lytic or non-lytic. The bacteriophages used in accordance with the present invention may be any bacteriophage, lytic or non-lytic, that is effective against a target bacterium of interest. The target bacteria may be any type of bacteria, for example but not limited to species and serotypes of, E. coli, Streptococci, Humicola, Salmonella, Campylobacter, Listeria, Staphylococcus, Pasteurella, Mycobacterium, Hemophilius, Helicobacter, Mycobacterium, Mycoplasmi, Nesseria, Klebsiella, Enterobacter, Proteus, Bactercides, Pseudomas, Borrelius, Citrobacter, Propionobacter, Treponema, Shigella, Enterococcus, Leptospirex, Bacillii including Bacillus anthracis and other bacteria pathogenic to humans, animal, fish, birds, plants. If desired, one of or a mixture or cocktail of identified differing bacteriophages may be used against a single bacterial target, or multiple bacterial targets.

The bacteriophage may be provided in a powder form as an immobilized bacteriophage preparation. For example, the bacteriophage may be adsorbed onto skim milk powder. Immobilized bacteriophage may be obtained from GangaGen Life Sciences Inc. (Ottawa, Canada).

By the term “encapsulated”, it is meant that the immobilized phages are coated with a substance that increases the phages' resistance to the physico-chemical stresses of its biotic or abiotic environment. The immobilized phages may be coated with a mixture of palmitic and stearic acids, present at a ration of 50:50, in accordance with the method described in US publication 2003/0109025 (Durand et al., which is incorporated herein by reference in its entirety). In this method, micro-drops of the coating substance are injected into a chamber containing the immobilized bacteriophages and rapidly cooled.

The coating layer exhibits a melting point between about 20° C. and about 120° C., for example between about 30° C. and about 80° C., or any temperature therebetween. If the coating substance is to be ingested or used for an oral application, then it is preferred that the substance is a food grade substance. An example of a coating substance comprises a mixture of stearic acid and palmitic acid present at a ratio of 50:50, for example, Stéarine 50/50™ (obtained from Exaflor, Gif sur Yvette, France). Other additive molecules may be added to the coating substance including antioxidants, sugars, or proteins.

In the encapsulated bacteriophage formulation of the present invention, the proportion of coating material in relation to the quantity of immobilized bacteriophages is between about 10% and about 99% by weight, or any amount therebetween, for example between about 30% and about 80%. For example, the proportion of coating material in relation to the quantity of immobilized bacteriophages may be about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 99% by weight, or any amount in a range defined by any two percentages just recited. This parameter may be adjusted according to the intended final application, depending on the desired rate of release of the immobilized bacteriophage composition.

The coating method uses a granulator (GLATT.™ granulator model CRG200). As would be known to a person of skill in the art, this device comprises a stainless steel chamber, the base of which is made up of a rotatable disc that is powered by a motor. An airflow is injected via the space between the base and the body of the chamber. The air escapes from the chamber through a filter placed in the upper portion of the chamber. The mass of immobilized bacteriophages is agitated by the rotation of the disc. A nozzle permits injection, by means of a pump, of the coating product kept at a temperature above its melting point in a temperature-controlled receptacle.

The coating substance is used in the granulator in a molten form. The temperature of the molten coating substance placed in the temperature-controlled receptacle can be about 30° C. and about 120° C., for example between about 60° C. and about 120° C., or any temperature therebetween; for example, the temperature of the coating substance may be 30, 35, 40, 45, 50, 55, 60, 65, 70 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120° C. or any temperature in a range defined by any two temperatures just recited. In any case, the temperature of the coating substance ought to be greater than the melting point of said coating substance, whether this is a pure product or a mixture. For example, the temperature of the coating substance may be at least about 5° C., or at least about 10° C. above the meting temperature of the coating substance.

The temperature of the air sweeping the granulation chamber is between about 10° C. and about 50° C., or any temperature therebetween; for example, the temperature of the, air may be about 10, 15, 20, 25, 30, 35, 40, 45, or 50° C. or any temperature in a range defined by any two temperatures just recited. The temperature of the air sweeping the granulation chamber is strictly controlled, so that at the moment of injecting the molten coating, the rise in temperature experienced by the immobilized bacteriophages does not exceed a few degrees, at maximum about 5° C.

The speed of rotation of the base plate and the rate of injection of the coating are interdependent parameters, connected to the mass of the products used. The speed of rotation is generally between about 50 and about 500 rpm (rotation per minute), or any speed therebetween; for example, the speed of rotation may be about 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, or 500 rpm, or any speed in a range therebetween. The injection of the coating can be carried out with the aid of one or more nozzles distributed over the periphery of the chamber.

The encapsulated bacteriophage formulation of the present invention exhibits desirable storage properties and may be used in a variety of applications. For example, which is not to be considered limiting in any manner, the antibacterial compositions may be used for human, veterinary, aquacultural, and agricultural applications. For example, the encapsulated bacteriophage formulation may be mixed with the feed of livestock, birds, poultry, domestic animals and fish, to aid in reducing the shedding of target bacteria.

The present invention will be further illustrated in the following examples.

EXAMPLES Example 1 Encapsulation of Bacteriophage Compositions

Immobilized bacteriophages using skim milk as the matrix, were obtained from GangaGen Life Sciences Inc (Ottawa, Canada), and encapsulated generally as described in US publication 2003/0109025 (which is incorporated herein by reference) using a GLATT™ granulator, model CRG200, with some modifications to preserve the activity of the phages. Briefly, 400 g of immobilized phages and 1.2 kg of vegetable fatty acids comprising palmitic and stearic acids and available as Stéarine 50/50™ (obtained from Exaflor, Gif sur Yvette, France) were used for encapsulation. The maximum temperature attained by the encapsulated phage preparation was 39° C.

Once the coating operation was complete, the encapsulated particles were collected and stored in airtight containers. The average particle size was between 100 and 1000 μm.

The effect of encapsulation on the titer of bacteriophages was determined by determining the activity of the immobilized phages before (“Before”, FIG. 1) and after (“After”, FIG. 1) encapsulation. For this analysis, encapsulated bacteriophages were re-suspended, and ground using a blender. The re-suspended encapsulated bacteriophages were blended in order to disrupt the encapsulated particles and release the bacteriophages. 0.5 g of encapsulated immobilized phage was mixed with 45.5 ml of re-suspension media (LB Broth or RO Water), and 250 μl of antifoam agent was added to prevent foaming upon grinding. The results of this analysis are shown in FIG. 1.

These results demonstrate that bacteriophages can be recovered from an encapsulated bacteriophage composition, and encapsulation does not inactivate the immobilized phage.

Example 2 Stability And Release of Encapsulated Bacteriophages

Phages were encapsulated as described in Example 1. The release of phages upon physical or chemical disruption was tested in the following manner: 0.5 g of encapsulated immobilized phage was mixed with 45.5 ml of re-suspension media (LB Broth or RO Water). 250 μl of antifoam agent was used to prevent foaming upon grinding. A control sample of encapsulated phages was prepared as described above, but not subjected to grinding, to determine the non-specific leaching of encapsulated bacteriophages within the re-suspension medium.

The stability of the encapsulated bacteriophages at low pH was also examined. After re-suspension (as outlined above), the encapsulated phages were incubated for 30 or 60 min at pH 2.15, neutralized to pH 7.0 using NaOH, then ground using a blender; another sample (control) was resuspended and immediately ground. Both the control and test samples were filter sterilized using a 0.45 μm syringe filter prior to use.

FIG. 2A shows the results of these analyses. The data show that resuspension of the encapsulated immobilized phage results in phage concentrations of about 1E+08 pfu/g. Similarly, incubation of the phages at pH 2.15 alone does not cause significant release of phages (phage concentration of about 3E+07 pfu/g after 30 minutes, or a phage concentration of about 4E+07 pfu/g after 60 minutes). However, following grinding and disruption of the encapsulated bacteriophage particles, the amount of phage released is about the same amount as was loaded onto the milk powder for immobilization (about 2E+09 pfu/g). Incubation of non encapsulated and non immobilized phages at pH 2.15 for 30 and 60 minutes however resulted in essentially complete loss of phage infectivity (FIG. 2B).

These results demonstrate that bacteriophages may be released following disruption of encapsulated bacteriophage particles. Furthermore, these results shows that encapsulated bacteriophage may be exposed to a pH of 2.15 for prolonged period of time, with little or no loss in activity (titer). The results for non-encapsulated and non-immobilized bacteriophages are consistent with the results of Jepson and March (2004, Vaccine, 22:2413-2419), where a dramatic loss of viability of bacteriophages was observed after only 5 minutes at pH below pH 2.2. This loss in activity is obviated by encapsulation of the bacteriophages as described in the present invention.

All citations are hereby incorporated by reference.

The present invention has been described with regard to one or more embodiments. However, it will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims. 

1. A method for producing an encapsulated bacteriophage formulation comprising, injecting a molten coating substance comprising stearic acid and palmitic acid at a ratio of 50:50 at a temperature of between about 20° C. and about 120° C. into a chamber containing bacteriophage immobilized on skim milk powder, the bacteriophage immobilized on skim milk powder agitated by rotation of a base of the chamber and swept by a flow of air at a temperature of between 10° C. and 50° C., the flow of air having a speed such that the chamber temperature is between about 30° C. to about 55° C., to produce an encapsulated bacteriophage formulation.
 2. The method according to claim 1, wherein the speed of rotation of the base of the chamber is between 50 and 500 rpm.
 3. The method according to claim 1, wherein the coating substance has a melting point of between 30° C. and 100° C.
 4. The method according to claim 1, wherein the injection temperature is between 60° C. and 120° C.
 5. The method according to claim 1, wherein the chamber temperature does not exceed by more than 5° C. a viability temperature of the immobilized bacteriophages.
 6. An encapsulated bacteriophage formulation comprising bacteriophage immobilized on skim milk powder and encapsulated with a coating substance comprising stearic acid and palmitic acid present at a ratio of 50:50. 